* {
  padding: 0px;
  margin: 0px;
}
body {
  background: #f3f3fe;
}
ul {
  list-style: none;
}

a {
  text-decoration: none;
}
// 头部
header {
  background: #fff;
  box-shadow: 0 5px 5px rgba(100, 100, 100, 0.3);
  border-bottom: solid 3px #1791a7;
  nav {
    padding: 20px 10px 40px 30px;
    width: 1200px;
    margin: 0 auto;
    ul {
      float: left;
      li {
        color: #555;
      }
    }
    div.button {
      float: right;
      width: 100px;
      background: red;
    }
  }
}
// 主体
main {
  width: 1200px;
  margin: 0 auto;
  margin-top: 20px;
  overflow: hidden;
  backgroud: red;
  article {
    height: 800px;
    width: 900px;
    box-sizing: border-box;
    border: solid 1px #ccc;
    background: greenyellow;
    float: left;
  }
  aside {
    box-sizing: border-box;
    border: solid 1px #ccc;
    width: 280px;
    height: 300px;
    float: right;
  }
}

//底部
footer {
  background: #fff;
  border-top: solid 1px #ddd;
  padding: 30px;
  margin-top: 30px;
  position: fixed;
  bottom: 0px;
  width: 100%;
  div {
    margin: 0 auto;
    text-align: center;
  }
}
